The plural form of the noun gadget is gadgets.
The plural possessive form is gadgets'.
Example: All of their gadgets' patents have been extended.
The possessive form of the singular noun gadget is gadget's.
Example: The gadget's inventor was very clever.
The plural possessive of gadget is gadgets'.
Quantum is singular, not singular possessive. The singular possessive form is quantum's.
The singular possessive form of "test" is "test's".
The singular possessive pronouns are "my," "mine," "your," "yours," "his," "her," and "its."
The singular possessive of "ant" is "ant's" and the plural possessive is "ants'".
Museum is singular. Museum's is singular possessive. Museums is plural. Museums' is plural possessive.
The singular possessive form of "classmate" is "classmate's."
Taco's is the singular possessive.
The singular possessive of dish is dish's
The singular possessive is Martin's.
The singular possessive is fish's.
Grave's is the singular possessive.